1. Field of the Invention
The present invention relates to a solar battery module which is easy to install, specifically to a solar module for use in a passive solar heating system in which solar heat energy is utilized by being converted into a heated flow of a thermal medium, particularly air.
2. Description of the Related Art
People in many regions in the world are now becoming acutely aware of environmental problems. In particular, mankind has strong apprehensions about the global warming phenomenon due to exhaust of CO.sub.2.
There is, therefore, an increasing demand for safe, clean energy sources. Presently a solar battery using a photoelectric conversion element is one of several promising clean energy sources because it is safe and easy to handle.
There are various types of solar batteries, such as:
(1) single crystal silicon solar cell,
(2) polycrystal silicon solar cell,
(3) amorphous silicon solar cell,
(4) copper-indium selenide solar cell, and
(5) compound semiconductor solar cell.
Recently, thin-film crystalline silicon solar cells, compound semiconductor solar cell and amorphous silicon solar cells among such cells have been studied and developed in various aspects because they can be formed a large-area elements at a comparatively low cost.
Japanese Patent Publication No. 48299/1991 discloses a passive solar system for utilizing a clean energy source, in which solar heat is collected by using a roof surface and is utilized for floor heating, hot-water supply, and the like. FIG. 8 shows an example of such a passive solar system, i.e., an air-heating type passive solar system. In the system shown in FIG. 8, fresh air enters a vent layer 804 formed on a roof board 803 through an outside air inlet 801 formed at the edge of an eaves and rises naturally and slowly toward the ridge of a roof while becoming warmer by receiving solar heat radiated to the roof surface through heat collecting metallic roofing plates 802. This warm air is supplied to a space formed under a floor via an air duct 807 by a fan 806, thereby to heat the entire space. The vent layer 804 and the air duct 807 are covered with a heat insulating material 805 in order to prevent heat from escaping.
The above-described air-heating type passive solar system utilizes solar heat as clean energy. However, the total amount of energy utilized by the system cannot be said to be obtained only from clean energy sources because it is necessary to use electrical power from a power line for the blower fan. Therefore, a method of using a solar cell, which is one of the existing clean energy sources, as a power source of the fan in the above-described system has been proposed. However, if the solar cell is mounted on the roof in an area away from the shingles or roof plates, it is necessary to increase the area of the roof. If the roof area is restricted, it is necessary to mount the solar cell in a different place. In such a case, an additional base for mounting the solar cell is required. In consideration of this problem, the applicants of the present invention have proposed a solar system in which a resin-molded type solar cell module, such as that shown in FIGS. 9(a) and 9(b), exhibiting more effective release of heat to the air in the vent layer is used in place of a metallic heat collecting plate.
FIGS. 9(a) and 9(b) illustrate an example of a solar system proposed by the applicants of the present invention. A solar cell module is mounted by nailing onto roofing members. This mounted structure is shown as an example in contrast to the conventional art and the present invention. FIG. 9(a) is a top-side perspective view and FIG. 9(b) is a cross-sectional view taken along the line 9b-9b' of FIG. 9(a). The drawings illustrate a solar cell 901, a surface cover member 902, a back insulating member 903, a back reinforcement member 904 which serves as a heating collecting surface, a filler member 905, roofing member 906 which also serves as a spacer, and nails 907. As illustrated, the solar cell module can be easily fixed on a roof by being nailed or stapled at a non-generating location. Thus, it is possible to mount the solar cell module on the roof without requiring a large change in the conventional architecture.
The solar system of this comparative example proposed by the applicants of the present invention, however, presents the problem of a possibility of the initial characteristics of the solar cell module being changed after use over a long period of time, i.e., about 20 years.
It is known, however, that the conversion efficiency of a solar cell is reduced if the ambient temperature is increased. If a solar cell is placed on a roof, and is kept at a high temperature, the photo-electric conversion efficiency is considerably reduced. In such a case, it is necessary to cool the solar cell to limit the reduction in conversion efficiency.